A passive keyless entry (PKE) system, offers an increased level of convenience over a standard lock and key, for example, by providing the ability to access a secure building or device without having to find, insert, and turn a traditional key. A user may simply approach a locked PKE lock and with little if any pause, the lock grants this user access if they are carrying an authorized token.
A PKE system is currently used in an automotive application and may offer increased convenience by identifying drivers and unlocking the car as they approach. Automotive access is traditionally given by inserting a key into the lock or by pushing buttons on a traditional remote keyless entry (RKE) system. In contrast, a PKE system grants access with reduced user interaction through the use of a token carried by the driver.
Several technical challenges have been encountered during the engineering of a radio frequency (RF) PKE system, for example, for use in a residential lock. The desired basic perceived behavior of the PKE system in a residential application may be as follows: 1) the user approaches and touches the lock; 2) the lock authenticates the user with a minimally perceived delay; 3) the lock unlocks; 4) the lock may not operate if the authorized user is outside a desired range and the lock is touched by another, unauthorized, user; 5) the lock may not operate if the authorized user is on the inside of the house, and the lock is touched on the outside by an unauthorized user; and 6) the battery powered lock needs months worth of battery life to prevent inconvenient and costly battery changes. 7) when an authorized user revokes a key from another user, it may be revoked within a timely manner.
Indeed, as will be appreciated by those skilled in the art, with respect to the above desired basic perceived behavior of the PKE system in a residential application, primary challenges to be addressed include items 2 (speed), 4 (distance), 5 (location), 6 (battery life), and 7 (timely revocation). Accordingly, it may be desirable to improve authentication speed, proximity measurement, location determination, decrease power consumption, and timely revocation processes for example.